Forwarding declaration issue

Question

I have:

// a.h
#pragma once
class B;
class A
{
public:
	void SomeMethod() const;
	B m_b;	// on stack
};
// a.cpp
#include "a.h"
#include "b.h"
void A::SomeMethod() const
{
	//
}
// b.h
#pragma once
#include "a.h"
class B
{
public:
	void OtherMethod(A const& a) const;
};
// b.cpp
#include "b.h"
void B::OtherMethod(A const& a) const
{
	//
}

Error: B m_b; is not recognized. If I put #include "b.h" in a.h file, I got forward declaration error. How can I overcome this?

Answer 1

For example, try this:

// a.h
#pragma once

#include "b.h" 

class A
{
public:
	void SomeMethod( ) const;
	B m_b;
};

// a.cpp
#include "a.h"

void A::SomeMethod( ) const
{
	//
}

// b.h
#pragma once

class A;

class B
{
public:
	void OtherMethod( A const& a ) const;
};

// b.cpp
#include <regex>
#include "a.h"
#include "b.h"

void B::OtherMethod( A const& a ) const
{
	//
}